A cooled turbine guide blade for a gas turbine is known from EP 1 505 256 A2. The turbine guide blade has a leading edge of a blade profile, a hot gas being capable of flowing onto said leading edge. A cooling duct running transversely with respect to the hot gas direction extends inside.
The calculation of the maximum permissible lifetime of gas turbine blades of this type, so as to ensure a fault-free and reliable operation of the gas turbine, is also carried out, taking into account the fatigue lifetime in terms of fatigue strength under short-term vibratory stresses (low-cycle fatigue=LCF). The LCF lifetime is determined on the basis of theoretical models and on the assumption of boundary conditions. After the maximum permissible lifetime is reached, the gas turbine is opened and the gas turbine blades are investigated visually and mechanically for defects, such as, for example, cracks. The investigation is intended to ascertain whether its further use for a next operating interval is possible, without the operation of the gas turbine being put at risk.
The dismantling of the gas turbine is complicated and leads to an undesirable increase in downtime. Furthermore, the investigations are time-consuming and cost-intensive, and therefore there is a general effort to reduce the downtimes of the gas turbine and increase the lifetime of the components used and employed.